Better error when process type does not exist (and in general on excon errors)

[schneems]

  1) This buildpack installs node and yarn and calls assets:precompile
     Failure/Error:
       app.run_multi("which node") do |out, status|
         expect(out.strip).to_not be_empty
         expect(status.success?).to be_truthy
       end

     Excon::Error::NotFound:
       Expected([200, 201, 202, 204, 206, 304, 429]) <=> Actual(404 Not Found)
     # /Users/rschneeman/.gem/ruby/2.7.2/gems/excon-0.78.0/lib/excon/middlewares/expects.rb:13:in `response_call'
     # /Users/rschneeman/.gem/ruby/2.7.2/gems/excon-0.78.0/lib/excon/middlewares/response_parser.rb:12:in `response_call'
     # /Users/rschneeman/.gem/ruby/2.7.2/gems/excon-0.78.0/lib/excon/connection.rb:456:in `response'
     # /Users/rschneeman/.gem/ruby/2.7.2/gems/excon-0.78.0/lib/excon/connection.rb:287:in `request'
     # /Users/rschneeman/.gem/ruby/2.7.2/gems/heroics-0.1.1/lib/heroics/link.rb:118:in `block in request_with_cache'
     # /Users/rschneeman/.gem/ruby/2.7.2/gems/rate_throttle_client-0.1.2/lib/rate_throttle_client/clients/exponential_increase_proportional_remaining_decrease.rb:17:in `call'

This is caused because there is no web process type on this app. We should include the path and the error message in the output:

$ heroku api PATCH /apps/hatchet-t-f1811bf539/formation/web --body '{"size": "Standard-1X"}'
PATCH api.heroku.com/apps/hatchet-t-f1811bf539/formation/web... 404
 ›   Error: Couldn't find that process type (web).
 ›
 ›   Error ID: not_found

This comes from the platform api which uses heroics